The present invention relates to alignment of a writing system and a workpiece. In particular, it relates to alignment to write a second layer pattern on a workpiece that has a first layer pattern, using an SLM. It extends to producing a mask or reticle, and to producing a layer of a device using the mask or reticle.
A variety of lithographic techniques have been developed that use a mask or reticle that has been patterned twice. The second patterning produces a phase shift structure.
It is increasingly important that the second patterning of the mask or reticle be accurately aligned to the first. This is particularly important with alternating phase shift structures, which may be produced in more than two patterning steps.
An opportunity arises to improve on alignment. Better alignment produces better masks or reticles or better device structures on substrates. Better masks or reticles are used to produce better layers of devices.